How to monitor health of tedge services
The health of tedge services like tedge-mapper, tedge-agent etc can be monitored via MQTT.
These services expose MQTT health endpoints which you can query to check if the process is still active or not.
To get the last known health status of a service you can subscribe to the following topic
te/<service-topic-id>/status/health
To refresh the health status of the service, publish an empty message on the topic below.
te/<service-topic-id>/cmd/health/check
If the response is not received then most likely the service is down, or not responding
For example, tedge-mapper-c8y publishes a message on topic te/device/main/service/tedge-mapper-c8y/status/health when it starts:
{ "pid": 290854, "status": "up", "time": "2023-04-02T21:37:12.345678901Z" }
| Property | Description |
|---|---|
pid | Process ID of the service |
status | Service status. Possible values are up or down |
time | Timestamp in RFC3339 format |
If the tedge service gets stopped, crashed, or killed, then a down message will be published on health status topic
and this will be retained until the service is restarted.
E.g. the mapper being killed:
- tedge
- mosquitto
- mqtt
tedge mqtt sub 'te/+/+/+/+/status/health'
mosquitto_sub -t 'te/+/+/+/+/status/health'
te/+/+/+/+/status/health
INFO: Connected
[te/device/main/service/mosquitto-c8y-bridge/status/health] 1
[te/device/main/service/tedge-mapper-c8y/status/health] {"pid":51367,"status":"down"}
[te/device/main/service/tedge-agent/status/health] {"pid":13280,"status":"up","time":"2023-02-02T09:37:47+00:00"}
Supported MQTT health endpoint topics​
The following endpoints are currently supported:
te/device/main/service/tedge-agent/status/healthte/device/main/service/tedge-mapper-c8y/status/healthte/device/main/service/tedge-mapper-az/status/healthte/device/main/service/tedge-mapper-aws/status/healthte/device/main/service/tedge-mapper-collectd/status/healthte/device/main/service/tedge-log-plugin/status/healthte/device/main/service/tedge-configuration-plugin/status/health
All future tedge services will also follow the same topic naming scheme convention.
Mosquitto bridge health endpoints​
The mosquitto bridge clients connecting thin-edge devices to the respective cloud platforms also report their health
status as retained messages to te/device/main/service/<mosquitto-cloud-bridge>/status/health topics. The health check
messages published by these clients are just numeric values 1 or 0, indicating active and dead bridge clients
respectively.
Here are the health endpoints of currently supported clouds, bridged with mosquitto:
| Cloud | Health topic |
|---|---|
| Cumulocity | te/device/main/service/mosquitto-c8y-bridge/status/health |
| Azure | te/device/main/service/mosquitto-az-bridge/status/health |
| AWS | te/device/main/service/mosquitto-aws-bridge/status/health |
Explicit health check requests via te/<bridge-service-topic-id>/cmd/health/check topics is not supported by these bridge clients.
Since the health status messages are sent as retained messages, just subscribing to these health topics is sufficient to get the latest status.